JP2001148650A - Radio base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the radio base station of an adaptive array system for preventing the generation of noise ('beegar' sound) from signals even in the case that a radio mobile station receives the signals transmitted to the other path-multiplexed mobile station. SOLUTION: In the case that the two mobile stations PS-A and PS-B are path-multiplexed, a clock generation part 52 generates a clock so as to shift the transmission time of a symbol to the mobile station PS-B for 0.5 symbol period to the transmission time of the symbol to the mobile station PS-A. By such adjustment of a transmission timing, in the mobile station, even at the time of receiving the symbol transmitted to the other path-multiplexed mobile station, since the reception time of the symbol is shifted from the reception time of the symbol to the present station, synchronization is not obtained, the received symbol to the other mobile station can not be demodulated as before and thus, meaningless noise ('beegar' sound) is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio base station of an adaptive array system for spatially multiplexing a transmission signal to a mobile station with different directivity patterns and transmitting the multiplexed signal.

[0002]

2. Description of the Related Art In recent years, digital communication equipment has transmitted information by modulating a carrier wave with a digital information signal (baseband signal) to improve transmission efficiency. 2. Description of the Related Art In digital communication, effective use of frequency resources has been achieved by increasing the transmission speed and increasing the number of channels accommodating a plurality of users on the same frequency by time division multiplexing. Further, a spatial multiplexing method that accommodates a plurality of channels at the same time at the same frequency by using the adaptive array method has attracted attention.

[0003] The adaptive array method is a method in which a directivity pattern (also called an array antenna pattern) is adaptively created by a plurality of antennas so that radio waves can reach only a user in a specific direction. For example, in the case of an adaptive array device having four sets of radio units each including a transmission circuit, a reception circuit, and an antenna, the amplitude and phase of a transmission signal are determined for each transmission circuit during transmission, and the amplitude and phase are determined for each reception circuit during reception. By adjusting each of them, it is possible to form respective directivity patterns at the time of transmission and at the time of reception. For details of the adaptive array method, see "Special Issue on Adaptive Signal Processing in the Spatial Domain and its Application Technology" (Transactions of the Institute of Electronics, Communication and Engineers, VOL.J75-B-IINO.11 NOVEMBE
R), detailed description is omitted here.

In an adaptive array type radio base station, by forming different directivity patterns for a plurality of mobile stations, a plurality of mobile stations can be multiplexed at the same time and communicate simultaneously with one frequency. . This communication uses path division multiple access (PDMA, Path Division Multiple).
iple Access, hereinafter referred to as path multiplexing. ) Called communication. This PDMA is described in "Path Division Multiple Access (P
DMA) mobile communication system ”(IEICE Technical Report RCS93-84 (1994-01),
pp. 37-44), so the details are omitted.

As described above, a radio base station using an adaptive array system can effectively use one wave (one frequency) by forming different directivity patterns.

[0006]

However, in a radio base station using the adaptive array system, when a mobile station assigned the same frequency and path-multiplexed approaches the mobile station, the mobile station will be connected to the other mobile station. Will pick up the signal sent to you. FIG. 9 is an explanatory diagram illustrating an example in which a mobile station receives a signal transmitted to another mobile station. In the figure, PS-A to PS-D indicate mobile stations, which are assumed to be assigned the same frequency. Numerals 31, 32, 33 and 34 shown by solid lines represent directivity patterns of communication channels directed to the mobile stations PS-A, PS-B, PS-C and PS-D, respectively.
Assuming that the PS-B moves as indicated by an arrow a in the figure, a situation occurs in which the moved PS-B receives a signal transmitted from the base station to the PS-A. Then, the PS-B demodulates a message sequence to the PS-A from the received signal, and generates a meaningless noise (beeger sound).
Will occur.

The reason is that the base station transmits a signal to be transmitted to a mobile station after performing a secret talk scrambling process so that the signal can be descrambled only by a secret key code unique to the mobile station held by the mobile station. Therefore, in the mobile station,
Only signals sent to the own station can be descrambled correctly, and signals to other mobile stations, even if they are received, are descrambled because the secret key code does not match. This is because it is converted and output as noise (beeger sound). Such beepering sounds are unpleasant and unpleasant for the user.

[0008] In order to prevent the generation of a beeger sound, before outputting a signal to a speaker on the mobile station side, it is determined whether the signal is a beagle sound or a voice using a frequency analysis technique or the like. If it is determined that the signal is a beeger sound, a method of not outputting the signal to the speaker may be considered. However, the determination means is difficult to achieve perfection, and it is necessary to mount the determination means on every mobile station, which impairs the simplicity of the mobile station.

Therefore, the present invention provides a mobile station that does not add the function of the mobile station, even if the mobile station receives a signal transmitted to another mobile station that is path-multiplexed. It is an object of the present invention to provide a radio base station that does not generate beeger sound from the signal.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a radio base station according to the present invention employs an adaptive array radio base station which spatially multiplexes a transmission signal to a mobile station with different directivity patterns and transmits the signal. And a multiplexing means for spatially multiplexing transmission symbols in transmission signals to the plurality of mobile stations with a predetermined time shorter than one symbol period.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Schematic Configuration of Radio Base Station> FIG.
FIG. 2 is a block diagram illustrating a configuration of a main part of the wireless base station according to the embodiment of the present invention. The radio base station is a radio unit 1
1, 21, 31, 41 and antennas 10, 20, 30,
40, a modem unit 60, a control unit 80, a baseband unit 70, and a signal processing unit 50. <Radio unit 11> The radio unit 11 includes a transmission unit 12 and a reception unit 1.
And 3. The transmitting unit 12 modulates the baseband signal (symbol data) input from the signal processing unit 50 to an intermediate frequency signal (hereinafter abbreviated as an IF signal),
The IF signal is converted into a high-frequency signal (hereinafter abbreviated as an RF signal), amplified to a transmission output level, and output to the antenna 10. The receiving unit 13 converts the received signal from the antenna 10 into an IF
The signal is converted to a signal and demodulated into a baseband signal (symbol data).

The radio units 21, 31, and 41 have the same configuration as the radio unit 11, and a description thereof will be omitted. <Modem unit 60> The modem unit 60 shifts the baseband signal by π / 4 shift QPSK (Quadrature Pha).
The modulation and demodulation are performed according to the (Shift Keying) method. <Control unit 80> The control unit 80 is specifically configured by a CPU and a memory, controls the entire wireless base station, and particularly when a call is received from a mobile station via a control channel, and
When an incoming call from the network is received, a communication channel is allocated to the mobile station. FIG. 2 shows an example of the assignment management table. In the allocation management table of FIG. 7, the horizontal direction indicates a communication channel by time division, and the vertical direction indicates multiplexing by path division. PS-A to PS-D in the column indicate the assigned mobile station. The figure shows a state in which PS-A, PS-C, and PS-D are time-division multiplexed, and PS-A and PS-B are path-multiplexed. <Baseband Unit 70> The baseband unit 70 connects to a network (public network or private network) (not shown) and connects a baseband signal to the telephone network 90.

The baseband unit 70 performs a time division multiplexing process. FIG. 3 shows a TDM for performing time division multiplexing.
FIG. 3 shows an explanatory diagram of an A / TDD frame. Here, a TDMA / TDD frame of a so-called PHS telephone system is shown. In the figure, T0 to T3 are transmission time slots, and R0 to R3 are reception time slots. The control channel (CCH in the figure) is constituted by a pair (T0, R0) of a transmission time slot and a reception time slot.
The communication channels TCH1, TCH2, and TCH3 are:
Each pair is constituted by a pair of (T1, R1), (T2, R2), (T3, R3). Communication channel TCH
1, TCH2 and TCH3 are distinguished by time division,
In each communication channel, a plurality of communication channels are further formed by path multiplexing.

The baseband unit 70 scrambles a baseband signal to be transmitted to a mobile station (user) using a pattern unique to the mobile station. The signal subjected to the secret-scramble processing is descrambled by the mobile station using a secret key code unique to the mobile station and can be returned to the original signal. Sound). <Signal Processing Unit 50> The signal processing unit 50 is mainly configured by a programmable digital signal processor, and includes a signal adjustment unit 51, a clock generation unit 52, and a response vector calculation unit 53.

The clock generator 52 generates a unique clock for each mobile station (user) to be path-multiplexed, and sends the generated clock to the signal adjuster 51. In the present embodiment, since the number of users to be path-multiplexed is two for simplification of description, the clock generation unit 52 generates the clock TA for the user A (see FIG.
(B). ) And a clock TB for user B (FIG. 6).
It is shown in (c). ). The clock generation unit 52
Normally, the clock TA and the clock TB are generated at the same time. However, when the response vector calculation unit 52 receives an instruction to shift the symbol transmission time because the direction of the user is close, the user A clock is generated by shifting the clock TB for B from the clock TA for user A by 0.5 symbol period.

The signal adjustment unit 51 generates symbol data for each user from the symbol data input from the radio units 11 to 41 and outputs the generated symbol data to the modem unit 60, and outputs the symbol data for each user transmitted from the modem unit 60. , Generates symbol data for each of the radio units 11 to 41 and outputs the symbol data to the radio units 11 to 41. FIG. 4 shows the signal adjustment unit 51.
FIG. 3 is a diagram showing the configuration of FIG. As shown in the drawing, the signal adjustment unit 51 includes a user processing unit 51 for each user to be path-multiplexed.
a, 51b. X1 to X4 and S1 to S4 in FIG.
Indicates a signal line or a terminal, but for convenience of description, it also indicates a symbol data name with which the signal line or the terminal is input / output. X1 to X4 indicate symbol data transmitted from the radio units 11 to 41 to the signal adjustment unit 51, and S1 to S4 are:
5 shows symbol data transmitted from the signal adjustment unit 51 to the radio units 11 to 41.

The user processing unit 51a includes radio units 11 to 41
Receives input of symbol data X1 to X4. The user processing unit 51a generates the symbol data Ua of the user A from the symbol data and outputs the symbol data Ua to the modem unit 60. Further, the user processing unit 51a receives an input of the symbol data Ua of the user A from the modem unit 60. The user processing unit 51a uses the symbol data to
It generates symbol data Sa1 to Sa4 for each of the elements 1 to 41, and outputs each symbol data to each wireless unit.
The other user processing units 51b also output the symbol data Sb1 to Sb4 to each wireless unit in the same manner. As a result, the wireless unit 11 stores the symbol data Sa from each user processing unit.
1 and Sb1 are added to the symbol data S1 (= Sa
1 + Sb1) will be sent.

Next, details of the processing by the user processing unit will be described. FIG. 5 is a diagram illustrating a configuration of the user processing unit 51a. The weight calculation unit 55 calculates the weight using the first few symbol data for each reception time slot. That is, the weight calculation unit 55 uses the symbol data X1 to X4 transmitted from the radio units 11 to 41 and the fixed symbol data D transmitted from the reference signal generation unit 506 according to the clock TA, and calculates E = D− (W
a1 × X1 + Wa2 × X2 + Wa3 × X3 + Wa4 × X
Weights Wa1 to Wa4 are calculated so as to minimize 4). The weights Wa1 to W calculated in this manner
a4 is used as an initial value in reception of the remaining symbol data of the reception time slot and in a transmission time slot that is a pair of the reception time slot.

When receiving a symbol, the weight calculating section 55 calculates the weights Wa1 to Wa calculated as described above.
4 is output in accordance with the clock TA. And a multiplier 5
21 to 524 and the adder 504, the symbol data Ua (= Wa1 × X1 + Wa2 × X2 +)
Wa3 × X3 + Wa4 × X4) is generated. The generated symbol data Ua for the user A is sent to the modem unit 60.

When transmitting a symbol, the symbol data Ua transmitted to the user A from the modem unit 60 is transmitted.
Are temporarily stored in the buffer 507. Buffer 50
7 outputs the symbol data Ua according to the clock TA generated by the clock generator 52. Weight calculator 5
3 are the weights Wa1 to Wa4 calculated as described above.
Is output in accordance with the clock TA. Multipliers 581-58
4 are symbol data Ua and weight Wa1
To Wa4, and symbol data Sa1 (= Wa1 × Ua) and Sa2 (= Wa2 × U) which are the multiplication results.
a), Sa3 (= Wa3 × Ua), Sa4 (= Wa4 ×
Ua) is output to the radio units 11 to 41.

The weight calculation unit of the user processing unit 51b
According to the clock TB, the weight is calculated and the weight is output when transmitting and receiving the symbol.
The buffer 1b outputs the symbol data Ub to the user B according to the clock TB. Here, since the directions of the user A and the user B are close to each other, if the clock generation unit 52 generates the clock TB with a delay of 0.5 symbol period from the clock TA, the clock TB is output from the user processing unit 51b. The symbol data Sb1 to Sb4 correspond to Sa1 to Sa4 output from the user processing unit 51a, respectively.
This is delayed by 5 symbol periods.

FIG. 6 is an explanatory diagram showing an example in which symbol data of one user is transmitted with a shift. As shown in the figure, two mobile stations PS-
A (user A) and PS-B (user B) are path-multiplexed and assigned, and these directions are close to each other. The clock generation unit 52 sends a clock TA to the user processing unit 51a, and sends a clock TB delayed by 0.5 symbol period to the clock TA to the user processing unit 51b. As a result, the symbol data sent to each user is shifted. A in FIG.
0, A1, A2, and A3 indicate symbol data transmitted toward PS-A, and B0, B1, B2, and B3 in FIG.
Indicates symbol data sent to PS-B.

By adjusting the symbol transmission timing, as described below, even if the mobile station receives the symbol data transmitted to the other mobile station that has been path-multiplexed, the symbol data is transmitted to the other mobile station. Is not synchronized with the transmission time of the symbol data to the own station (accordingly, the reception time), the synchronization is not synchronized, and the symbol data to the other mobile station received is not synchronized. Does not demodulate correctly. If there is such a demodulation error, the descrambling of the demodulated symbol (voice signal) is stopped, so that it is possible to prevent the generation of meaningless noise (beeger sound). In other words, the most important point of the present invention is that the radio base station transmits a symbol by changing the symbol transmission time for each mobile station so that even if the mobile station receives a signal of another mobile station, it cannot demodulate correctly. It is a big feature. <Response Vector Calculator 52> Response Vector Calculator 50
Calculates a response vector indicating the direction from the base station to the mobile station from the symbol data input from the radio unit 11. The method for calculating the response vector will be described below. The response vector to the user A is represented by Ra = (h _1A , h _2A , h _3A ,
h _4A ) ′, and the response vector to the user B is Rb = (h
_1B , _h2B , _h3B , _h4B ) ', and R = (Ra, Rb). Symbol data X1 to X from radio units 11 to 41
4, X = (X1, X2, X3, X4) ′. Also, U = (Ua, Ub) ′ using Ua and Ub calculated by the signal adjustment unit 51. Then X =
Since the RU relational expression holds, the response vector calculation unit 53
Is a response vector Ra to each user using X and U,
Calculate Rb. The response vector includes information indicating the direction of the user (mobile station) from the base station. When the directions are similar, the mobile station can easily receive a signal transmitted to another mobile station. Therefore, the response vector calculation unit 53 determines that the difference between the direction of the user A and the direction of the user B is small. When the value falls below a certain value, the clock generation unit 52
An instruction is sent to delay the generation time of the user TB clock TB with respect to the generation time of the user A clock TA.

Next, the processing of the radio mobile station that receives the signal transmitted from the radio base station will be described. <Configuration of Radio Mobile Station> FIG. 7 is a block diagram showing a configuration of a main part of the radio mobile station in the embodiment of the present invention.

The radio mobile station includes a radio section 200, an antenna 250, a signal processing section 220, and a voice output section 240. <Radio unit 200> The radio unit 200 includes a modulator 202, a transmission circuit 201, a switch 205, and a reception circuit 203.
And a demodulator 204. <Timing Unit 210> The timing unit 210 includes a synchronization adjusting unit 211 and a clock generating unit 212. <Synchronization Adjustment Unit 211> The synchronization adjustment unit 211 adjusts the clock generation time by the clock generation unit 212 so that the received and demodulated message string matches the synchronization word.

The synchronization adjustment unit 211 always checks the match between the synchronization word and the message sequence even after the synchronization adjustment is completed. If the synchronization word does not match, the synchronization adjustment unit 211 re-adjusts the synchronization. 222 is notified of the loss of synchronization. <Clock Generation Unit 212> The clock generation unit 212 generates a clock based on an instruction from the synchronization adjustment unit 211. The demodulator 204 demodulates the message sequence in accordance with the clock.

Here, taking demodulation by the mobile station PS-A as an example, when a signal transmitted to the other mobile station PS-B that has been path-multiplexed is received, the signal is demodulated with an error. The process will be described. Demodulator 20
4 indicates that the I component and the Q
Get the components and FIG. 8 shows the I component subjected to synchronous detection. Although not shown, the Q component can be represented by a similar diagram.

The mobile station PS-A is to generate a synchronous clock for each symbol period to obtain a I _k. T ₁ of the drawing -
t ₄ is the generation time of the synchronous clock of PS-A. The demodulator 204 outputs I _{1 to} I ₄ by these synchronous clocks.
= {0.5, -0.25, -0.75, 0.75}. Thereafter, at time t _M , the mobile station PS-A
It is assumed that the vehicle has moved to a point where the strength of the transmission signal directed to PS-B is strong, for example, by approaching −B. As a result, the mobile station PS-A may receive a path-multiplexed signal directed to another mobile station PS-B without receiving a signal directed to the PS-A from the base station.

The PS-A demodulates the signal with the same synchronization clock as before even after the movement. T ₅ ~t ₉ of the figure, PS
−A is the synchronous clock generation time. Demodulator 204 is
By these synchronous clocks, I ₅ (F) to I ₉ (F)
= {-0.75,0,0.75, -0.25,0.5}
To get. However, as described in the signal processing unit 50 of the radio base station, the transmission time of the symbol data transmitted from the base station to the PS-B is 0.5 symbol times longer than the transmission time of the symbol data transmitted to the PS-A. Since it is shifted by the period, the original signal to PS-B is from t ₅ ′
Signals I ₅ (T) to I ₉ (T) at t ₉ ′ = {0.5, −
0.25, 0.5, -0.5, 0.75 °.

As described above, the mobile station acquires an erroneous I _k (F) without acquiring the original I _k (T) transmitted to another mobile station. The mobile station will get an erroneous Q _k (F) for similar reasons. By the way, the following relationship exists between I _k and Q _k and the message sequence. Message sequence {a ₁ , a ₂ ,..., _An , a _{n + 1} ,.
(A _n , a _{n + 1} ) corresponds to the binary data string (X _k , Y _k ). Then, the binary data sequence (X _k , Y _k ) and I _k ,
The following relational expression holds between Q _k .

I _k = I _{K -1} cos [θ (X _k , Y _k )]-Q
_k−1 sin [θ (X _k , Y _k )] Q _k = I _K−1 sin [θ (X _k , Y _k )] + Q _k−1 cos
[Θ (X _k , Y _k )] When θ = −3π / 4, X _k = 1, Y _k = 1 When θ = 3π / 4, X _k = 0, Y _k = 1 θ = π / 4 , X _k = 0, Y _k = 0, θ = −π / 4, X _k = 1, Y _k = 0 Based on the above equation, I _k , I _k−1 , Q _k , Q _{k− From (1)} , a binary data sequence (X _k , Y _k ) is obtained, from which a message sequence a _n
Is obtained.

Therefore, due to the errors in I _k and Q _k as described above, the message sequence a _n is naturally converted to an incorrect message sequence. As a result, synchronization may be lost due to the demodulated message sequence being different from the synchronization word, or a CRC error may occur even if the synchronization words match. <Signal Processing Unit 220> The signal processing unit 220 includes an error determination unit 221, a control unit 222, and a descrambling processing unit 2.
23. <Error judging unit 221> The error judging unit 221 applies a CRC to the message sequence transmitted from the radio unit 200.
A check is performed, and the presence or absence of an error is notified to the control unit 222. <Control Unit 222> The control unit 222 receives the notification of the loss of synchronization from the synchronization adjustment unit 211 or the error determination unit 2
When the error notification is received from 21, the descramble processing unit 223 stops descrambling of the message string. <Descramble Processing Unit 223> The descramble processing unit 223 descrambles the message sequence sent from the wireless unit 200. Since the message sequence sent to other mobile stations has lost synchronization and errors,
There is an instruction to stop descrambling from the control unit 222, and the descramble processing unit 223 does not descramble the message sequence. Therefore, the descrambling processing unit 223
Does not descramble message strings to other mobile stations whose secret key does not match. <Audio Output Unit 240> The audio output unit 240 is composed of a speaker, and outputs a message sequence (audio signal) descrambled by the descramble processing unit 223. The descrambling unit 223 descrambles only the message string whose secret key matches, so that there is no meaningless noise (ie, beeger sound) descrambled by the wrong secret key. .

As described above, the radio base station according to the present embodiment performs a process of shifting the transmission time of the symbol to be transmitted to the path-multiplexed mobile station by an appropriate time within one symbol period. By adjusting the transmission timing in this way, the mobile station cannot correctly demodulate the original symbol from the received signal even if it receives a symbol transmitted toward the other path-multiplexed mobile station. Demodulate the wrong symbol. As a result, it is possible to prevent the generation of meaningless noise (beeger sound) in the mobile station.

It should be noted that the present invention is not limited to the above embodiment, and the following modified examples are of course included in the present invention. (Modification 1) In the present embodiment, adjustment of transmission timing when two mobile stations are path-multiplexed has been described, but the present invention is not limited to this. For example, three mobile stations (PS-1, PS-2,
When PS-3) is path-multiplexed, the transmission time of the symbol data to PS-2 is shifted by 0.33 symbol period from the transmission time of the symbol data to PS-1. By shifting the transmission time of the symbol data to -3 by 0.33 symbol periods, it is possible to make it easier for the mobile station to erroneously demodulate the symbol data sent to another mobile station.

Similarly, when N paths are multiplexed, the transmission time of each symbol is generally represented by K / N.
(K = 0, 1, 2,..., N−1) × T (symbol period)
It can be. Furthermore, without being limited to one symbol period, for example, one symbol period
It is also possible to adjust the transmission timing so as to shift the symbol period, the 1.5 symbol period, or the 2 symbol period. For example, if it is shifted by one symbol period, the value of the original symbol data will be correctly demodulated,
The sequence of demodulated symbols can be shifted. That is, since the original symbol sequence _{{a 0, a 1, a} 2, ...} are transmitted shifted by one symbol period, the mobile station, {a _1,
By incorrectly demodulated as _{a 2, a 3, ...}} , falling off the symbol a _0, and mismatch of synchronization word, CRC
An error can be generated. (Modification 2) In the present embodiment, the symbol transmission timing is adjusted when the directions of two path-multiplexed mobile stations are similar. However, regardless of the direction of the mobile station, The transmission timing may be constantly adjusted.

When a large number of antennas are provided and the number of multiplexes that can be path-multiplexed is increased, the transmission times of symbols to each mobile station are close to each other. Is difficult to demodulate erroneously. Therefore,
When the number of multiplexed paths is small, the transmission timing is always adjusted. When the number of multiplexed paths is large,
The transmission timing may be adjusted by focusing on a set of mobile stations having similar directions.

[0037]

The radio base station according to the present invention is an adaptive array type radio base station for spatially multiplexing a transmission signal to a mobile station with different directivity patterns and transmitting the multiplexed signal. The transmitted symbols in the signal are
Multiplexing means is provided for spatially multiplexing by shifting by a predetermined time shorter than the symbol period.

According to this configuration, the radio base station adjusts the transmission timing such that the transmission time of symbols to the plurality of spatially multiplexed mobile stations is shifted by a predetermined time shorter than one symbol period. Therefore, even if a mobile station receives a signal transmitted to another mobile station, the symbol is correctly demodulated because the synchronous clock for acquiring the symbol is different from the synchronous clock for acquiring the symbol for the mobile station. Can not. As a result, it is possible to prevent the generation of meaningless noise (beeger sound) in the mobile station.

Here, the multiplexing means converts each of the transmission symbols to the n mobile stations into k / n (k = 0, 1, 2,.
.. Are spatially multiplexed while being shifted by a time of (n-1) × T (one symbol period). According to this configuration, the present radio base station adjusts the transmission timing so that the transmission times of the symbols to the spatially multiplexed mobile stations are not as close as possible. On the other hand, in the mobile station, it is possible to avoid a situation in which the synchronization time at which the symbol is captured is close to the synchronization time of the other mobile station, and as a result, the symbols of the other mobile station are correctly demodulated.

The radio base station of the present invention is an adaptive array type radio base station for spatially multiplexing a transmission signal to a mobile station with different directivity patterns and transmitting the multiplexed signal, based on a signal received from the mobile station. Means for calculating a direction vector of the mobile station with respect to the base station, and transmission symbols in transmission signals of a plurality of mobile stations whose direction vectors are similar to each other by shifting the transmission symbols by a predetermined time shorter than one symbol period. Multiplexing means for spatial multiplexing.

According to this configuration, the present radio base station adjusts the transmission timing for a group of mobile stations approaching from the base station. When the number of spatially multiplexed mobile stations is large, the transmission times of symbols to each mobile station are close to each other, so that the mobile station correctly demodulates symbols of other mobile stations with its own synchronization clock. A situation arises. This radio base station adjusts the transmission timing by limiting the target to mobile stations that are likely to pick up signals to other mobile stations, so that the transmission time of symbols to each mobile station is close. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a main part of a wireless base station according to an embodiment of the present invention.

FIG. 2 shows an example of an assignment management table.

FIG. 3 is an explanatory diagram of a TDMA / TDD frame for performing time division multiplexing.

FIG. 4 is a diagram showing a configuration of a signal adjustment unit 51.

FIG. 5 is a diagram illustrating a configuration of a user processing unit 51a.

FIG. 6 is an explanatory diagram showing an example in which symbol data of one user is transmitted with a shift.

FIG. 7 is a block diagram illustrating a configuration of a main part of the wireless mobile station according to the embodiment of the present invention.

FIG. 8 shows an I component that is synchronously detected.

FIG. 9 is an explanatory diagram showing an example in which a mobile station receives a signal transmitted to another mobile station.

[Description of Signs] 10 to 40 antennas 11 to 41 radio unit 12 transmission unit 13 reception unit 50 signal processing unit 51 signal adjustment unit 51a, 51b user processing unit 52 clock generation unit 53 response vector calculation unit 60 modem unit 70 baseband unit Reference Signs List 80 control unit 90 telephone network 200 radio unit 201 transmission circuit 202 modulator 203 reception circuit 204 demodulator 205 switch 210 timing unit 211 synchronization adjustment unit 212 clock generation unit 220 signal processing unit 221 error determination unit 222 control unit 223 descramble processing unit 240 Audio output unit 250 Antenna 504 Adder 505 Weight calculation unit 506 Reference signal generation unit 507 Buffer 521 to 524 Multiplier 581 to 584 Multiplier

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04J 15/00 H04B 7/26 BF Term (Reference) 5J021 AA05 AA06 CA06 DB02 DB03 EA04 FA17 FA20 FA21 FA24 FA26 FA32 GA01 GA08 HA05 HA10 5K022 FF00 5K059 CC02 CC04 DD31 5K067 AA24 AA33 CC01 EE02 EE10 GG01 HH21 KK02

Claims (3)

[Claims] An adaptive array radio base station for spatially multiplexing a transmission signal to a mobile station with a different directivity pattern and transmitting the multiplexed transmission signal, wherein transmission symbols in the transmission signals to the plurality of mobile stations are mutually exchanged. A radio base station comprising multiplexing means for spatially multiplexing by shifting by a predetermined time shorter than one symbol period. 2. The multiplexing means converts each of transmission symbols to n mobile stations into k / n (k = 0, 1, 2,... N−
2. The radio base station according to claim 1, wherein spatial multiplexing is performed by shifting by 1) × T (one symbol period). 3. An adaptive array radio base station for spatially multiplexing a transmission signal to a mobile station with different directivity patterns and transmitting the multiplexed signal, wherein the base station of the mobile station is based on a signal received from the mobile station. Means for calculating a direction vector with respect to, and multiplexing means for spatially multiplexing transmission symbols in transmission signals of a plurality of mobile stations whose direction vectors are approximate to each other by shifting them by a predetermined time shorter than one symbol period. A wireless base station comprising: